TOOLS FOR CLEANER PROCESSES IN TANZANIA
P.P.A.J. VAN SCHIJNDEL AND F.J.J.G. JANSSEN1
This article focuses on tools for cleaner production processes with emphasis on two Tanzanian industries. First a
description of a process and ways to improve it in an economically and environmentally friendly manner are given.
Secondly, tools to survey processes are discussed like exergy analysis, pinch analysis and environmental Life Cycle
Assessment. Furthermore, some practical results from an environmental audit and exergy analysis in the soap and
cement manufacturing industry in Tanzania are summarised.
The authors are at the Centre for Environmental Technology (CMT), Faculty of Chemistry and Chemical
Engineering, Eindhoven University of Technology, STO 3.25, P.O.Box 513, 5600 MB, Eindhoven, The
Netherlands, Email: p.p.a.j.v.Schijndel@tue.nl, respectively f.j.j.g.Janssen@kema.nl
The World is in a continuous state of change. There is
an increase in global economy and world population,
which may endanger earth as an ecosystem. The
answer against this threat is called sustainable
There are several definitions of sustainable
development, which are abstract and can be
interpreted differently. Commonly used definitions
include the one given by the World Commission on
Environment and Development (WCED, 1987) in the
‘Humanity has the ability to make development
sustainable - to ensure that it meets the needs of the
present without compromising the ability of future
generations to meet their own needs. The concept of
sustainable development does imply limits - not
absolute limits but limitations imposed by the present
state of technology and social organisation of
environmental resources and by the ability of the
biosphere to absorb the effects of human activities’.
In this concept of sustainable development by the
WCED, there are three dimensions: environment,
development and security.
2. CLEANER PRODUCTION
Cleaner production of materials, goods and services is
one of the answers for sustainable development. It
means production in a way in which resources and
energy are used in an efficient way and only small
amounts of waste and emissions are produced. Other
important factors are the use of renewable resources
and the increase in quality of the products. This
doesn’t mean that the cleaner production concept is
different from that of an economic approach,
minimising costs and maximising profits. Because
minimising the use of resources and in this way also
cutting back on emissions will decrease the costs of a
Some other important issues used in this context are
source (raw material) reduction, waste reduction and
pollution prevention (Allen and Rosselot, 1997). From
Table 1, it becomes clear that there are differences
between these similar issues.
Table 1: Comparison of different issues
Yes No No
/ No Yes Yes
Yes Yes No
-) Not applicable
#) Reduction of solid and liquid wastes
*) Not necessarily
Source: Allen and Rosselot (1997)
Energy carriers belong to the most important resources
for mankind. The production of energy sources can
cause many environmental problems like major
accidents, water pollution, maritime pollution, land
use and siting impact, radiation and radioactivity,
solid waste disposal, hazardous air pollution,
deterioration of ambient air quality, acid deposition,
stratospheric ozone depletion, and global climate
change. These problems may be decreased when the
energy efficiency of processes is increased. Thus there
is a need for cleaner production processes.
3. CLEANER INDUSTRIAL PROCESSES
An industrial process can be simply outlined, as in
Figure 1. The process can be seen as a black box.
Resources and energy (work) are the inputs and
products, wastes, emissions (air, soil, water), excess
heat etc. are the outputs of this process.
Figure 1. Schematical drawing of an industrial
For the energy input, one may need to add a separate
black box, representing the fact that energy carriers
are converted into electricity, power or heat before
being used in the actual process, as shown in Figure 2.
Figure 2. Schematical drawing of an energy
In both Figures 1 and 2 there are possibilities for in-
process recycling. It means some waste products can
be separated from the waste stream and used again as
resources. For instance waste heat can be used to make
steam. Cleaner production for the two Figures means
that there should be a decrease of resources used and
an increase of useful products.
The traditional way to improve processes towards a
more sustainable production uses costly waste
treatment facilities added-on at the stack or discharge
pipe of the manufacturing plant; so called end-of-pipe
treatment. Sometimes end-of-pipe treatment is
unavoidable. Looking closer at waste reduction in, and
not at the end of the process, it becomes clear this is
much cheaper and more sustainable than the ordinary
separation procedures using filters, scrubbers, settlers
etc. (Allen and Rosselot, 1997).
Other disadvantages of end-of-pipe treatment are:
• It takes resources to remove pollution;
• Pollution removal generates residues;
• It takes more resources to disperse residues;
• Disposal of residues also produces pollution.
It thus becomes clear that there must be a focus on the
process as a whole and not only at the pipes leaving
the process or the plant. Several ways to improve
processes into cleaner production processes are (from
simple to more difficult):
• improve a process by optimisation procedures, like
• Use of other resources, of higher quality, with less
• Improve some process units;
• Process integration;
• Total change towards more sustainable processes.
In the next sections, tools for checking the energy
efficiency and environmental impact of a process and
possible solutions to increase efficiency and decrease
environmental impact are discussed.
There are several tools available to check, for a given
process, whether there are possibilities to decrease the
environmental impact. For most chemical and physical
processes thermodynamics provide a powerful tool,
because thermodynamics can forecast the amount of
resources and energy used and sometimes emissions
produced within a certain process (Swaan Arons and
Kooi, 1993). Two thermodynamically related tools
discussed here are exergy analysis and pinch analysis.
Another, non-thermodynamic, tool discussed here is
environmental Life Cycle Assessment, shortly LCA.
Exergy analysis is much familiar with the enthalpy or
energy analysis. The difference is that in exergy
analysis entropy is applied, contrary to energy
analysis, which only includes enthalpy. An exergy
analysis can be performed for a whole plant or for
different unit operations. Information about exergy
analysis can be found in literature, Szargut et al.
(1988) and Kotas (1995).
The following definition for exergy is used normally:
‘Exergy is the maximum amount of work that can be
obtained from a stream of matter, heat or work as it
comes to equilibrium with a reference environment,
and is a measure of the potential of a stream to cause
change, as a consequence of not being completely
stable relative to the reference environment. Exergy is
not subject to a conservation law, but it is destroyed
due to irreversibility’s during any process.’
A basic example is the possibility of converting
mechanical work into heat with 100% efficiency. Heat
has a lower exergy, compared with work - exergy is
also called quality of energy. Heat can not be
converted into work by 100% efficiency, since heat has
a lower quality compared with work. Some examples
of the difference between energy and exergy are shown
in Table 2. From this table hot water and steam with
the same enthalpy have different exergy or quality
values. Steam has a higher quality than hot water.
Fuels like natural gas and gasoline have exergetic
values comparable to their net combustion value.
Work and electricity have the same exergy as
enthalpy. Exergy can be calculated by product of
energy and quality.
Table 2: Examples of energy and exergy of
Water 80°C 100 16 0.16
Steam 1 bar and 120°C 100 24 0.24
Natural Gas 100 99 0.99
Electricity / work 100 100 1.00
The advantage of exergy analysis over an ordinary
energy analysis is the fact that an exergy analysis is
more accurate and scientifically correct, because:
• Exergy analysis provides a better view on the
efficiency of a process;
• Exergy analysis is very useful to find the unit
operation where efficiency improvements are the
most suitable or useful.
Each process designer or process engineer should
perform an exergy analysis to make all exergy losses
visible in the process under study. The method is very
powerful when comparing improvement solutions in
an objective and quantitative manner. Of course the
exergy analysis does not give direct answers on how to
improve the process but it gives the best clues where to
start, namely at the point where the largest exergy
Exergy analysis is also used in the design phase and
during optimisation of processes. It is a very useful
tool when used for comparison of different production
routes of a specific product.
Using the knowledge from exergy analysis it becomes
clear that, for instance, a heat exchanger can be
optimised by increasing its heat-exchanging surface,
because this decreases the temperature difference, ΔT,
of the heat-exchanger at the same heat load conditions.
At the same time costs will go up with increasing heat
exchanging surface. Therefore there will be an
economical/exergetical optimum as visualised in
Figure 3. Heat exchanger optimisation
Pinch analysis is designed for the optimisation of Heat
Exchanger Networks (HEN) by matching excess of
heat and cold streams in a system (Linnhoff and
Alanis, 1991). An economical analysis is also included
in the optimisation phase. Experiences (Varwijk et al.,
1998) show that using pinch analysis energy savings
from 20%-40% are possible with pay back periods less
than three years.
Heat exchanger surface
The theory behind pinch technology is quite simple.
For a process all hot and cold streams are inventoried;
cold streams are the streams that need to be heated and
hot streams need cooling. Necessary data are
temperatures, flows and heat/cooling duty. A diagram
is made with the hot composite and the cold
composite, with temperature at y-axis and the enthalpy
on the x-axis (see Figure 4). The cold and hot
composites may be moved horizontally until the two
curves are very close together at one point. This point
is called the pinch point; the temperature difference
ΔT at this pinch is often chosen to be an offset value of
about 10°C. When the optimal situation is calculated
from the diagram, an improved HEN can be designed.
An important rule of thumb for HEN design is not to
perform a heat exchange process from above to below
the pinch point.
Figure 4. Composite curve with pinch point
The area between the hot and cold composite
temperature represents an exergy loss, which can of
course be lowered by decreasing ΔT to a minimal
value. It appears that pinch analysis is a good tool to
improve a given HEN for certain conditions. But for a
given process, exergy analysis is a much more
powerful tool as shown in Wall and Gong (1996) and
in two articles (Gaggioli et al., 1991 and Linhoff and
Alanis, 1991). In the last two articles pinch and exergy
analysis were used to optimise a given process for
nitric acid production. Pinch analysis led to a good
optimisation, however the optimisation exergy analysis
gave a two times higher efficiency than found by pinch
Life Cycle Assessment or LCA
The Environmental Life Cycle Assessment is used to
improve the environmental impact of products and
services but can also be used to improve processes.
The LCA of a product studies the environmental
aspects and potential impacts throughout a product’s
life cycle, (i.e. from cradle-to-grave) from raw material
acquisition through production, use and disposal. In
contradiction to exergy and pinch analysis, LCA looks
at all environmental impacts instead of only problems
related to energy use.
LCA’s of production processes can be of interest
because they are useful for comparison with other
production processes in order to distinguish an
environmental ranking. Four steps have to be carried
out to perform a LCA (Balkema, 1998; Guinée et al.,
1993a and b):
1. Goal and scope definition to define the study focus
2. The inventory analysis; which consists of a
thorough mass balance over the production
3. An impact assessment; in which all the emissions
and resource uses are translated to environmental
4. Interpretation of the results.
Environmental effects used in LCA include ozone
layer depletion, greenhouse effect, smog formation,
eutrophication, toxic effects for humans and the
ecosystem and resource depletion. In this article it is
not possible to give an elaborate discussion of all the
advantages and disadvantages. Instead of this, a case is
presented (Kniel et al., 1996).
Case: The Nitric Acid Plant.
This example describes the use of LCA for the
improvement of a nitric acid plant. In this process NH3
is converted into NO2 which dissolves into water
forming HNO3. Because this process is not so efficient,
a lot of NOX (NO and NO2) is emitted. There are two
effects from this deficiency, high production cost for
HNO3 and eutrophication and acidification through
the NOX emission. Two solutions presented in the
article (Kniel et al., 1996) are (1) end-of-pipe
treatment of NOX with ammonia in which N2 and H2O
are formed or (2) cleaner production methodology by
reaction at a higher pressure to increase the efficiency
in which the NO2 is absorbed to form HNO3.
Both methods have the same aim, although method (2)
is cheaper because it is more efficient in point of view
of the product. In method (1) NH3 is used twice in the
process, both as reactant for HNO3 and as the end-of-
pipe treatment compound. It is also notable that during
the production of NH3 one important emission
compound is NOX. The amount of acidification and
eutrophication for process (2) is lower than for process
(1). The conclusion of this case, based on LCA:
cleaner production in process is much better than end-
Although the usefulness of this tool has been proved,
some scepticism on LCA’s carried out will always
exist. Without proper data or good set-up of the studies
the outcome of the LCA will be of low quality.
Another important tool is the ‘Common Sense’ of the
engineer. The process has to be seen as a total not just
as a sum of separate processes.
Combination of all the tools presented here can
provide an even more powerful tool.
It is possible to give a summary of some common
• Alter the production technique: Use techniques that
produce less waste and/or also use less resources.
• Alter the resources used; do not use resources
which contain material that will be wasted at the
end of the process. For instance paints without
solvents (powder paints) will not emit solvents
during application and curing. Use resources with
less waste and less toxic components.
• Alter the process management; better maintenance
methods, better training for operators.
5. OPTIONS FOR TANZANIAN INDUSTRIES
Like is the case for all industries World-wide, there
are a lot of opportunities for the Tanzanian industries
to improve the quality of production. The efficiencies
in use of both resources and energy can increase.
There is room as well to decrease effects on the
environment, like air, water and noise pollution.
The advantages from cleaner production can be very
generous; production costs can drop and make room
for more possibilities for improving the processes. At
the same time security and health conditions at and
around the plant will improve. And in almost all cases
the increase in process efficiency will decrease
emissions to air, water as well as the amount of solid
Ydhego (1993) stresses the fact that there should be
put more emphasis on waste reduction and cleaner
production rather than on end-of-pipe technologies
because of the high costs for these technologies. In
order to stimulate cleaner production there must be
facilities for training etc. The establishment of the
Cleaner Production Centre of Tanzania (CPCT),
located at the offices of the Tanzania Industrial
Research & Development Organisation, TIRDO, in
Dar Es Salaam is one of the first steps to introduce
cleaner production in Tanzania. In the past there has
also been a first cleaner production programme called
CEPITA, cleaner production in Tanzania, the results
of which are being audited at this time. Next steps are
to educate the engineers and scientist to think in terms
of environmental friendly processes, as is intended in
the courses at UCLAS (University College of Land &
Architectural Studies), and the start of a M.Sc. course
in environmental engineering at UDSM (University of
Dar es Salaam). A Centre for Environmental Science
and Technology at UDSM is planned for beyond the
year of 2000. Some examples of cleaner production in
Tanzania are listed below.
One of the companies involved in the cleaner
production programme of CPCT in 1997 was the
‘Mshindi’ soap factory. Located in an area with a low
capacity sewerage system they managed to modify the
process into a ‘zero’ waste production plant. The only
wastewater they now have comes from sanitary
systems, like toilets, showers and kitchen. They are
planning to treat this water using a heliophyt filter on
site (Van Schijndel, 1997). Other options being carried
out are: better truck offloading system to decrease
spillage, increased amount of steam pipes in the soap
tank to decrease steam use, use of other raw materials,
effluent recycling filter to decrease disposable waste
and the increase of overall power factor to decrease
electricity consumption (CPCT, 1998).
In 1997 an exergy analysis was performed at the Wazo
Hill cement factory at kiln number three to check if
such an analysis was possible with scarce data. The
analysis proved to be possible. An exergetic efficiency
of 37% was calculated for the existing process; there
were plenty of possibilities for further improvement to
43% efficiency with pay back times less than 1.5 years
(Van Schijndel et al., 1998). Improvement options
include improvement of the pre-heater system and
installation of a pre-calciner (20% less fuel),
improvement of the dust filters (5% less fuel) and
better kiln isolation (4% less fuel). Other options are
the installation of new burners, isolation of the heat
exchangers and preheating of the fuel. Note that an
increase in exergetic efficiency decreases the demand
for heavy fuel oil and therefore puts less pressure on
Three tools for cleaner production have been
discussed. Pinch analysis can be used in a good way to
optimise heat exchanger networks, however exergy
analysis appears to be a more powerful tool than pinch
analysis. LCA on processes shows to be a suitable tool
when focusing on environmental effects, however
there still exists some scepticism about the method. A
combination of the tools mentioned, including
common engineering sense, may prove to be a much
more powerful tool for cleaner production.
Allen, D.T and Rosselot, K.S. (1997), “Pollution
prevention for chemical processes”, John Wiley&
Sons, New York.
Balkema, A.J. (1998), “Sustainability criteria for
technology comparison”, proceedings of 11th
European Junior Scientist Meeting, 12-15 February
1998, Wildpark Eekholt, Germany, pp.1-7.
Cleaner Production Centre of Tanzania, CPCT (1998),
“Cleaner Production Demonstration Project at
Shivji&Sons Limited”, unpublished research report.
Gaggioli, R.A., Sama, D.A., Sanhong Qian, El-Sayed,
Y.M. (1991), “Integration of a new process into an
existing site: A case study in the application of exergy
analysis”, Journal of Engineering for Gas Turbines
and Power, Vol.113, pp.170-183.
Guinée, J.B., Heijungs, R., Udo de Haes, H.A.,
Huppes, G. (1993), “Quantitative life cycle assessment
of products, 1 Goal definition and inventory”, J.
Cleaner Production, Vol.1, No.1, pp.3-13.
Guinée, J.B., Heijungs, R., Udo de Haes, H.A.,
Huppes, G. (1993), “Quantitative life cycle assessment
of products, 2 classification, valuation and
improvement analysis”, J. Cleaner Production, Vol.1,
Kniel, G.E., Delmarco, K., Petrie, J.G. (1996), “Life
Cycle Assessment Applied to Process Design:
Environmental and economic analysis and
optimization of a nitric acid plant”, Environmental
Progress, Vol.15, pp.221-228.
Kotas, T.J. (1995), “The Exergy Method of Thermal
Plant Analysis”, 2nd
edition, Krieger publishing
Linnhoff, B. and Alanis, F.J. (1991), “Integration of a
new process into an existing site: a case study in the
application of pinch technology”, Journal of
Engineering for Gas Turbines and Power, Vol. 113,
Swaan Arons, J. de, Kooi, H.J. van der (1993),
“Exergy Analysis. Adding insight and precision to
experience and intuition”, Precision Process
Szargut, J., Morris, D.R., Stewart, F.R. (1988),
“Exergy Analysis of Thermal, Chemical, and
Metallurgical Processes”, 1st
edition, Springer Verlag,
Van Schijndel, P.P.A.J. van (1997), unpublished
Van Schijndel, P.P.A.J. van, Boer, J. den, Janssen,
F.J.J.G., Mrema, G.D., Mwaba, M.G. (1998), “Exergy
analysis as a tool for energy efficiency improvements
in the Tanzanian and Zambian industries”, ICESD
Conference Engineering for sustainable development,
1998, University of Dar Es Salaam,
Varwijk, J.W.M., Dekker, E. den, Sonderkamp T.
(1998), “Pinchtechnologie, effectieve manier van
besparen”, NPT Procestechnologie, pp. 36-38 (in
Wall, G. and Gong, M. (1996), “Exergy Analysis
versus Pinch Technology”, Proceedings ECOS’96:
“Efficiency, Costs, Optimization, Simulation and
Environmental Aspects of Energy Systems”,
The World Commision on Environment and
Development,WCED (1987), “Our Common Future”,
Oxford University Press, New York.
Yhdego, M. (1993), “Cleaner production in
Tanzania”, UNEP Industry and Environment, pp.37-
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